Silver halide photographic light-sensitive material

Abstract: A silver halide photographic light-sensitive emulsion is disclosed. The photographic material comprises a support and a silver halide emulsion layer provided on the support, and at least 30 % of the total projection area of the silver halide grains contained in the silver halide emulsion layer is occupied by that of tabular silver halide grains having an aspect ratio of not less than 2; and the support comprises polyethylene-2-6-naphthalate and has a thickness of 70 µm to 120 µm. The photographic material is inhibited in the formation of roller mark in an automatic processor.

Description: The present invention relates to a black and white silver halide photographic light-sensitive material of high sensitivity which has little pressure fogging and which has few roller marks even in hardening-free high temperature rapid processing. In the field of medical photographic light-sensitive materials, in particular, high sensitivity and high image quality are essential requirements of patient disease diagnosis. It is known to use tabular silver halide grains to achieve high sensitivity and high image quality. Tabular grains offer advantages such as improved spectral sensitization efficiency and improved image granularity and sharpness, and are disclosed, for instance, in British Patent No. 2,112,157 and US Patent Nos. 4,439,520, 4,433,048, 4,414,310 and 4,434,226. However, tabular silver halide grains are faulty in that fogging is likely when they are compressed. As means of overcoming this drawback, some methods have been proposed in which silver halide grains are prepared having a core of higher iodine content or incorporating a latex. However, the former approach does not offer a perfect solution because of pressure desensitization, resulting in nothing more than a balance between mutually opposite features called pressure blackening and pressure desensitization. The latter approach has drawbacks such as deterioration of the driability of the light-sensitive material upon processing because of the increased amount of binder. Also, methods of eliminating the hardening in the course of processing are disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) Nos. 111933/1983 and 206750/1988, in which tabular silver halide grains are used at a hydrophilic colloid layer swelling rate below 200%. In fact, the driability improves and the degree of hardening can be lowered when tabular grains are used at a hydrophilic colloid layer swelling rate of not higher than 200%. However, hardener-free processing results in an extremely increased number of roller marks, or roller pressure traces occurring in the developer, so that no satisfactory results are obtained solely by reducing the light-sensitive material swelling rate below 200%. JP-2089045 discloses a silver halide light sensitive material comprising a polyester film substrate and silver halide emulsion layers. JP-61205137 discloses a biaxially oriented polyester film for eletrophotographic materials which is prepared by coating a polyester film with a coating agent containing polyester, including isophthalic and aromatic dicarboxylic acid residues. Colour silver halide photographic light-sensitive materials comprising polyethylene naphthalate as support and having a thickness falling within the range of from 70 to 120 µm are disclosed in EP-A-0583787, EP-A-0588331, EP-A-0607905, EP-A-0606070 and EP-A-0601501. All of these documents were published on or after the present filing date, and fall within the terms of Article 54(3) EPC. The object of the present invention is to provide a black and white silver halide photographic light-sensitive material of high sensitivity, high image quality and improved pressure resistance which has no roller marks even when processed with a hardener-free developer. The above-described object of the invention is accomplished by a black and white silver halide photographic light-sensitive material comprising a support and a first silver halide emulsion layer provided on the support in which at least 30 % of the total projection area of the silver halide grains contained in the silver halide emulsion layer is occupied by the projection area of tabular silver halide grains having an aspect ratio of not less than 2; and the support comprises polyethylene-2,6-naphthalate and has a thickness of from 70 µm to 120 µm. The average grain size of the tabular silver halide grains relating to the present invention is preferably from 0.3 to 3.0 µm, more preferably from 0.5 to 1.5 µm. The average value, average aspect ratio, of grain diameter/thickness, aspect ratio, of the tabular silver halide grains of the present invention is not less than 2.0, preferably from 2.5 to 20.0, more preferably from 3 to 10.0. The average thickness of the tabular silver halide grains of the present invention is preferably from 0.01 µm to 0.5 µm, more preferably from 0.04 µm to 0.3 µm. In the present invention, the diameter of a silver halide grain is defined as the diameter of a circle having the same area as the projected area of the grain as observed on an electron micrograph of the grain. In the present invention, the thickness of a silver halide grain is defined as the least distance between two parallel planes constituting the tabular silver halide grain. The thickness of a tabular silver halide grain can be obtained from an electron micrograph shadowed with the silver halide grain or an electron micrograph of a sampled cross-section of the silver halide grain in an emulsion coated and dried on the support. To obtain the average aspect ratio, at least 100 grains are sampled. With respect to the silver halide emulsion of the present invention, the effect of the invention is obtained when tabular silver halide grains account for not less than 30% of all light-sensitive silver halide grains, and the effect is enhanced when the ratio of tabular silver halide grains is not less than 50%. The emulsion for the present invention may be a single emulsion or a mixture of two or more emulsions. When used in the form of a mixture, the emulsion of the present invention may be combined with the same kind of emulsion or with grains of normal crystal habit or twin grains having an aspect ratio of less than 2. The silver halide photographic light-sensitive material of the present invention may be configured with a single emulsion layer or a number of emulsion layers. Even in the case of a multiple-layer structure, the desired effect of the invention is obtained, as long as grains having an aspect ratio of not lower than 2 occupy not less than 30% of the total projection area of all light-sensitive silver halide grains. The tabular silver halide emulsion used in the present invention is preferably a monodispersed emulsion, with greater preference given to a tabular silver halide emulsion comprising silver halide grains whose variation coefficient of grain size distribution (σ/ r ) is 0.2 or less. In the above, σ is the standard deviation of grain size distribution and r is the average grain size. The tabular silver halide emulsion used in the present invention may have any halogen composition such as silver chloride, silver bromide, silver chlorobromide, silver iodobromide and silver chloroiodobromide. From the viewpoint of high sensitivity, silver bromide or silver iodobromide is preferred, the average silver iodide content being from 0 to 5.0 mol%, preferably from 0.1 to 3.0 mol%. The tabular silver halide grains used in the present invention may have a uniform halogen composition or localized silver iodide, with preference given to a halogen composition wherein silver iodide is localized in the core. A tabular silver halide emulsion can be produced in accordance with Japanese Patent O.P.I. Publication Nos. 113926/1983, 113927/1983, 113934/1983 and 1855/1987 and European Patent Nos. 219,849 and 219,850. A monodispersed tabular silver halide emulsion can be produced in accordance with Japanese Patent O.P.I. Publication No. 6643/1986. A tabular silver iodobromide emulsion having a high aspect ratio can be produced by adding an aqueous solution of silver nitrate to a gelatin solution containing a halide or simultaneously adding both an aqueous solution of silver nitrate and an aqueous solution of a halide to an aqueous solution of gelatin being kept at a pBr of not more than 2, to form a seed crystal, and growing the seed crystal by adding a silver nitrate solution and a halide solution by the double jet method. The size of tabular silver halide grains can be controlled by temperature and rates of addition of the aqueous solutions of silver salt and halide during grain formation. The aspect ratio can be controlled by method of seed crystal preparation, thickness of seed crystal, grain growing pAg and pH, halide composition, ripening time, temperature and other factors. The average silver iodide content of a tabular silver halide emulsion can be controlled by changing the composition of the aqueous halide solution added, i.e., the ratio of the bromide and iodide. In producing tabular silver halide grains, a silver halide solvent such as ammonia, thioether or thiourea can be used as necessary. For grain growth, the halogen and silver may be supplied as fine grains of silver halide, though they may be supplied in an aqueous solution containing silver ions and an aqueous solution containing halogen ions. In such case, silver iodide, silver iodobromide, silver bromide, silver chlorobromide, silver chloride, a solution containing halogen ions and a solution containing silver ions may be combined. For the silver halide emulsion relating to the present invention, core/shell grains or double-structure grains, wherein the silver halide composition varies between the core and surface may be used. Methods of core/shell emulsion production are described in detail in US Patent Nos. 3,505,068 and 4,444,877, British Patent No. 1,027,146 and Japanese Patent O.P.I. Publication No. 14331/1985. The core/shell grain is herein defined as a grain wherein the silver iodide content of the outermost layer is less than 5 mol%, preferably less than 3 mol%. The silver iodide content of the outermost layer of a silver halide grain can be determined by various methods of surface elemental analysis. It is advantageous to use such methods as XPS (X-ray photoelectron spectroscopy), Auger electron spectroscopy and ISS. The silver iodide content of the outermost layer of the present invention is defined on the basis of measurements obtained by XPS, the simplest method of high precision. Maximum thickness analyzable by the XPS surface analysis method is about 10 Å. For the principles of the XPS method for iodine content analysis near the silver halide grain surface, see "Denshi no Bunko" (spectroscopy of electron), Jyunichi Aihara et al., Kyoritsu Library 16, published by Kyoritsu Shuppan, 1978. The above-described emulsion may be of any of the surface latent image type, wherein latent images are formed on the grain surface, the internal latent image type, wherein latent images are formed inside the grain, and the type wherein latent images are formed in and on the grain. These emulsions permit the use of cadmium salt, lead salt, zinc salt, thallium salt, ruthenium salt, osmium salt, iridium salt or complex thereof, rhodium salt or complex salt, or the like, at the stage of physical ripening or grain preparation. To remove soluble salts, the emulsion may be washed by noodle washing, flocculation precipitation or the like. Preferred washing methods for desalinization include the method described in Japanese Patent Examined Publication No. 16086/1960, which uses an aromatic hydrocarbon series aldehyde resin containing the sulfo group, and the method described in Japanese Patent O.P.I. Publication No. 158644/1988, which uses example polymeric flocculants G3 and G8. Chemical sensitization can be achieved by sulfur sensitization, sensitization with Se compounds, sensitization with Te compounds, gold sensitization, sensitization with noble metals in group VIII of the periodic table of elements, e.g., Pd, Pt, Id, and combinations thereof. The combination of gold sensitization and sulfur sensitization and the combination of gold sensitization and sensitization with Se compounds are preferred. It is also preferable to use reduction sensitization in combination with chemical sensitization. From the viewpoint of sensitivity and dye adsorption, it is preferable to supply iodine ions during or upon completion of chemical sensitization, in the form of silver iodide grains, in particular. It is also preferable to carry out chemical sensitization in the presence of a compound adsorbable to silver halide. For this purpose, preference is given to compounds having the mercapto group or the benzene ring, such as azoles, diazoles, triazoles, tetrazoles, indazoles, thiazoles, pyrimidines and azaindenes. With respect to the silver halide photographic light-sensitive material relating to the present invention, the silver halide emulsion may be reduced for reduction sensitization by, for example, the addition of a reducing compound, silver ripening, wherein the emulsion is subjected to a condition involving excess silver ions at pAg of from 1 to 7, and high-pH ripening, wherein the emulsion is subjected to a high pH condition at a pH of from 8 to 11. These methods may be used in combination. The reducing compound addition method is preferred, since the degree of reduction sensitization can be precisely adjusted. The reducing compound may be an organic or inorganic compound, exemplified by thiourea dioxide, stannous salts, amines, polyamines, hydrazine derivatives, formamidinesulfinic acid, silane compounds, borane compounds, ascorbic acid and derivatives thereof and sulfites, with greater preference given to thiourea dioxide, stannous chloride and dimethylamineborane. The appropriate range of the amount of these reducing compounds added is from 1 x 10 -8 to 1 x 10 -2 mol per mol of silver halide, though the amount varies depending on the reductivity of the compound, kind of silver halide, dissolution conditions and other factors. These reducing compounds are added in solution in an organic solvent such as water or alcohol during silver halide grain growth. It is also preferable to reduce an optional portion and/or layer of the silver halide grain other than the outermost layer and further grow the grain. From the viewpoint of effect control, it is preferable that such reduction be performed on the inner core surface for multiple-layer lamination, e.g., the seed emulsion grain surface or the core surface when grains are not being grown. This reducing treatment may be performed in the presence of a thiosulfonic acid compound as disclosed in Japanese Patent O.P.I. Publication No. 135439/1990 and 136852/1990. The silver halide photographic light-sensitive material of the invention may be optically sensitized with methine and other spectral sensitizing dyes, including cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar dyes, hemicyanine dyes, styryl dyes and hemioxonol dyes. Especially useful dyes are cyanine dyes, merocyanine dyes and complex merocyanine dyes. These spectral sensitizing dyes can have any heterocyclic ring nucleus which is generally used for dyes. Examples of such nuclei include the pyrroline nucleus, oxazoline nucleus, thiazoline nucleus, pyrrole nucleus, oxazole nucleus, thiazole nucleus, selenazole nucleus, imidazole nucleus, tetrazole nucleus, pyridine nucleus and nuclei resulting from condensation of these nuclei with an aliphatic hydrocarbon ring, such as an indolenine nucleus, a benzindolenine nucleus, an indole nucleus, a benzoxazole nucleus, a naphthoxazole nucleus, a benzothiazole nucleus, a naphthothiazole nucleus, a benzoselenazole nucleus, a benzimidazole nucleus and a quinoline nucleus. These nuclei may be substituted on a carbon atom. The merocyanine dye or complex merocyanine dye may have a 5- or 6-membered heterocyclic nucleus such as a pyrazolin-5-one nucleus, a thiohydantoin nucleus, a 2-thioxazolidine-2,4-dione nucleus, a thiazolidine-2,4-dione nucleus, a rhodamine nucleus or a thiobarbituric acid nucleus as a nucleus having a ketomethylene structure. These dyes are described in German Patent No. 929,080, US Patent Nos. 2,231,658, 2,493,748, 2,503,776, 2,519,001, 2,912,329, 3,655,394, 3,656,959, 3,672,897 and 3,649,217, British Patent No. 1,242,588 and Japanese Patent Examined Publication No. 14030/1969. These sensitizing dyes may be used singly or in combination. Sensitizing dyes are often used in combination. Typical combinations are described in US Patent Nos. 2,688,545, 2,977,299, 3,397,060, 3,522,052, 3,527,641, 3,617,293, 3,628,964, 3,666,480, 3,679,428, 3,703,377 and 3,837,862, British Patent No. 1,344,281 and Japanese Patent Examined Publication No. 4936/1968. Sensitizing dyes may be added at any optionally chosen time during grain formation by coating, before, during and after chemical sensitization, and may be preferably added at a number of time points. The light-sensitive material of the present invention may have a crossover cut layer between the support and the emulsion layer. The crossover cut layer may be a subbing layer between the support and the hydrophilic colloid layer. A dye layer may be formed between the subbing layer and the emulsion layer. Dyes used in the subbing layer include oxonol dyes having the pyrazolone nucleus or barbituric acid nucleus, azo dyes, azomethine dyes, anthraquinone dyes, allylidene dyes, styryl dyes, triarylmethane dyes, merocyanine dyes and cyanine dyes. The dye used in the dye layer may be dispersed in the form of fine particles. Dyes which can be used for this purpose include Example Compounds 2, 4, 6, 8, 9, 10, 11, 12, 13-27, -2, 5, 6, -3, 4, 6, 8, 9, 10, 11, 12, 14-28, -3, 5, 6, 8, 10-16, -3, 5, 6, 7 described on pages 6 through 12 of Japanese Patent O.P.I. Publication No. 264247/1990. These dyes can easily be synthesized in accordance with International Patent Publication No. 88/04794, European Patent Nos. 027423A1, 276,566 and 299,435, Japanese Patent O.P.I. Publication Nos. 92716/1977, 155350/1980, 155351/1980, 205934/1986 and 68623/1973, US Patent Nos. 2,527,583, 3,486,897, 3,746,539, 3,933,798, 4,130,429 and 4,040,841. Although gelatin can be used as a hydrophilic colloid or binder in the light-sensitive material of the present invention, non-gelatin hydrophilic colloids may also be used. Such non-gelatin hydrophilic colloids include gelatin derivatives, graft polymers of gelatin and other polymers, proteins such as albumin and casein, cellulose derivatives such as hydroxyethyl cellulose, carboxymethyl cellulose and cellulose sulfates, sugar derivatives such as sodium alginate, dextran and starch derivatives, and various synthetic hydrophilic homopolymers or copolymers such as polyvinyl alcohol, partially acetalized polyvinyl alcohol, poly-N-vinylpyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinylimidazole and polyvinylpyrazole. It is particularly preferable to use a dextran or polyacrylamide having a weight average molecular weight from 5000 to 100000 in combination with gelatin. Examples of such case are disclosed in Japanese Patent O.P.I. Publication No. 307738/1989, 62532/1990, 24748/1990, 44445/1990, 66031/1989, 65540/1989, 101841/1988 and 153538/1988. Gelatins include limed gelatin, acid-processed gelatin, enzyme-processed gelatin as described on page 30 of Bull. Soc. Sci. Phot., Japan, No. 16 (1966), and gelatin derivatives obtained by reacting gelatin with various compounds such as acid halides, acid anhydrides, isocyanates, bromoacetic acid, alkanesultones, vinylsulfonamides, maleinimide compounds, polyalkylene oxides and epoxy compounds. Polyethylene-2,6-naphthalate, the support for the silver halide photographic light-sensitive material of the present invention, is described below. The polyethylene-2,6-naphthalate mentioned herein is a polymer substantially consisting of ethylene-2,6-naphthalate units, but may be an ethylene-2,6-naphthalate polymer modified with a small amount, e.g., not more than 10 mol%, preferably not more than 5 mol% of a third component. Polyethylene-2,6-naphthalate is usually produced by condensing naphthalene-2,6-dicarboxylic acid or a functional derivative thereof such as methyl naphthalene-2,6-dicarboxylate, and ethylene glycol under appropriate reaction conditions in the presence of a catalyst. The third component is exemplified by dicarboxylic acids such as adipic acid, oxalic acid, isophthalic acid, terephthalic acid, naphthalene-2,7-dicarboxylic acid and diphenyl ether dicarboxylic acid or lower alkyl esters thereof, dicarboxylic acids such as p-oxybenzoic acid and p-ethoxybenzoic acid or lower alkyl esters thereof, dihydric alcohols such as propylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and diethylene glycol, and polyalkylene glycols such as polyethylene glycol and polytetramethylene glycol. This polymerization may be carried out in the presence of lubricants such as titanium dioxide, stabilizers such as phosphoric acid, phosphatidic acid and esters thereof, antioxidants such as hindered phenol, polymerization regulators and plasticizers. Preferably, the polyethylene naphthalate for the present invention has a intrinsic viscosity number of not lower than 0.4, preferably from 0.40 to 0.65. The intrinsic viscosity number can be measured by a Ubbelohde's viscometer. The degree of crystallinity is preferably not lower than 35% and not higher than 60% for obtaining good physical properties after film forming. The crystallinity degree is measured by a density-gradient-column method and defined according to the following equation: Crystallinity degree = (ρ (100) -ρ/ρ (100) -ρ (0) ) x 100% in the above, ρ = Density of the material measured ρ (100) = Density of the material in a perfect crystal form ρ (0) = Density of the material in an amorphous form The support of the invention of polyethylene-2,6-naphthalate film can be prepared by a known method. The film may be stretched lengthwise and widthwise simultaneously or successively, and the stretching may be performed by 2 steps or more to each direction of length and width. In the present invention, the thickness of the support comprised of polyethylene-2,6-naphthalate is from 70 to 120 µm. The formation of scrach marks and roller marks in the light-sensitive material using tabular silver halide grains with a high aspect ratio of 2 or more are prevented by the use of the above polyethylene-2,6-naphthalate film having a thickness within the above range. Since the commercial value of the polyethylene-2,6-naphthalate film of the present invention decreases when dust adheres thereto upon use, its surface resistivity is preferably not higher than 1014 Ω·cm. To obtain such a film, various methods are used as appropriate, including the method in which an antistatic agent is coated, the method in which a thin layer of a metal or metal compound is formed on the film surface, the method in which an antistatic agent is added at polymerization of the starting materials for polyester, and the method in which the starting materials for polyester and an antistatic agent are mixed at film preparation. It is also acceptable to use polyethylene-2,6-naphthalene as obtained by polymerization condensation of the starting materials sodium alkylbenzenesulfonate and polyalkylene glycol. The support surface may be subjected, for example, to subbing, corona discharge, ultraviolet irradiation to facilitate coating layer adhesion. The silver halide emulsion relating to the present invention may incorporate various photographic additives added before or after physical ripening or chemical ripening. Such additives include those described in Research Disclosure Nos. 17643 (December 1978), 18716 (November 1979) and 308119 (December 1989) (hereinafter referred to as RD17643, RD18716 and RD308119, respectively). The following table shows where the additives are described. Additive RD17643 RD18716 RD308119 Page Category Page Category Page Category Chemical sensitizer 23 III 648 upper right 996 III Sensitizing dye 23 IV 648-649 996-998 IV Desensitizing dye 23 IV 998 B Dye 25-26 VIII 649-650 1003 VIII Developing accelerator 29 XXI 648 upper right Antifogging agent/stabilizer 24 IV 649 upper right 1006-1007 VI Brightening agent 24 V 998 V Hardener 26 X 651 left 1004-1005 X Surfactant 26-27 XI 650 right 1005-1006 XI Antistatic agent 27 XII 650 right 1006-1007 XIII Plasticizer 27 XII 650 right 1006 XII Lubricant 27 XII Matting agent 28 XVI 650 right 1008-1009 XVI Binder 26 XXII 1003-1004 IX EXAMPLES Example 1 Preparation of support After an ester exchanging reaction catalyst was added to 100 parts of dimethyl naphthalene-2,6-dicarboxylate and 60 parts of ethylene glycol, 1.2 parts of sodium dodecylbenzenesulfonate, 0.8 parts of polyethylene glycol having a molecular weight of 8000 and 0.01 part of thyroid were added, followed by polymerization condensation. The polymer thus has a obtained intrinsic viscosity number of 0.50 and a crystallinity degree of 45%. The resulting polyethylene-2,6-naphthalate was fused and extruded and 3 fold stretched at 140°C and then transversely 3 fold stretched at 155°C. A temperature of 255°C was maintained for 10 seconds. A 100 µm film was thus obtained. Supports of 70 µm, 120 µm and 180 µm thickness were prepared at different degrees of elongation. Subbing Each support was subbed in the same manner as for sample No. 9 in Example 1 of Japanese Patent O.P.I. Publication No. 104913/1977. Preparation of emulsions A to C Preparation of seed emulsion While maintaining a temperature of 60°C, a pAg of 8 and a pH of 2.0, monodispersed cubic grains of silver iodobromide having an average grain size of 0.3 µm and a silver iodide content of 2 mol% were prepared by the double jet method. The resulting reaction mixture was desalinized at 40°C, using an aqueous solution of Demol-N (produced by Kao Atlas) and an aqueous solution of magnesium sulfate, after which it was redispersed in an aqueous gelatin solution, to yield a seed emulsion. Grain growth from seed emulsion Using the above seed emulsion, grains were grown as follows: First, the seed emulsion was dispersed in an aqueous gelatin solution being kept at 40°C, and aqueous ammonia and acetic acid were added to obtain a pH of 9.7. An aqueous solution of ammoniacal silver nitrate and an aqueous solution of potassium bromide and potassium iodide were then added to the dispersion by the double jet method, while maintaining a pAg of 7.3 and a pH of 9.7, to yield a layer containing 35 mol% silver iodide. Next, another aqueous solution of ammoniacal silver nitrate and an aqueous solution of potassium bromide were added by the double jet method. Until 95% of the desired grain size was reached, the pAg was kept at 9.0, the pH being varied continuously over the range from 9.0 to 8.0. The pAg was then changed to 11.0, and while keeping the pH at 8.0, grains were grown until the desired grain size was obtained. Subsequently, acetic acid was added to obtain a pH of 6.0, and the silver electrode potential was adjusted to +25 mV of E Ag using an aqueous solution of potassium bromide. Then the anhydride of 5,5'-dichloro-9-ethyl-3,3'-di-(3-sulfopropyl)-oxacarbocyanine sodium salt (dye A) and the anhydride of 5,5'-di-(butoxycarbonyl)-1,1'-diethyl-3,3'-di-(4-sulfobutyl)-benzimidazolocarbocyanine sodium salt (dye B), at 300 mg and 15 mg per mol of silver halide, respectively, were added as spectral sensitizing dyes. Next, to remove the excess salts by precipitation, the mixture was desalinized with the above aqueous solution of Demol-N and aqueous solution of magnesium sulfate, and then stirred and re-dispersed in an aqueous solution containing 92.2 g of ossein gelatin. Monodispersed silver iodobromide emulsions A, B and C, comprising tetradecahedral grains with round tips having an average silver iodide content of 2.0 mol%, were thus prepared, which had average grain sizes of 0.40 µm, 0.65 µm and 1.00 µm and coefficients of variance of grain size (δ/ r ) of 0.17, 0.16 and 0.16, respectively, and aspect ratios of these emulsions, are all 1.0. In the above, δ is the standard deviation of grain size distribution and r is the average grain size of the emulsion. Preparation of emulsions D through F Preparation of spherical seed emulsion A monodispersed spherical seed emulsion was prepared by the method of Japanese Patent O.P.I. Publication No. 6643/1986. Solution A Ossein gelatin 150 g Potassium bromide 53.1 g Potassium iodide 24 g Water was added to make a total quantity of 7.2 l. Solution B Silver nitrate 15000 g Water was added to make a total quantity of 6 l. Solution C Potassium bromide 1327 g 1-phenyl-5-mercaptotetrazole (dissolved in methanol) 1.2 g Water was added to make a total quantity of 3 l. Solution D Aqueous ammonia (28%) 705 ml To solution A being vigorously stirred at 40°C, solutions B and C were added by the double jet method over a period of 30 seconds, whereby nuclei were formed. During this operation, pBr was kept between 1.09 and 1.15. 1 minutes and 30 seconds later solution D was added over a period of 20 seconds, followed by ripening for 5 minutes at a KBr concentration of 0.071 mol/l and an ammonia concentration of 0.63 mol/l. Then the seed emulsion was adjusted to pH 6.0 and immediately desalinized and washed. Electron microscopy identified this seed emulsion as a monodispersed spherical emulsion having an average grain size of 0.26 µm and a distribution width or δ/ r value of 18%. Preparation of grown emulsion The resulting spherical seed emulsion, at 0.14 mol per mol of the silver in the desired grown emulsion, was dissolved and dispersed in a 65°C aqueous solution of gelatin containing polypropyleneoxy-polyethyleneoxy-disuccinate sodium salt, after which dimethylamineborane was added to a concentration of 1 x 10 -5 mol per mol of the silver in the finished silver halide emulsion. Subsequently, a silver nitrate solution, adjusted to a final average silver iodide content of 0.50 mol%, and a halide solution of potassium bromide and potassium iodide were added by the controlled double jet method over a period of 43 minutes, while maintaining a pH of 2.0, a pAg of 8.0 and a temperature of 65°C. In this operation, the silver potential was adjusted to + 25 mV using an aqueous solution of potassium bromide. Then the above-mentioned dyes A and B, at 300 mg and 15 mg per mol of silver halide, respectively, were added as spectral sensitizing dyes. Next, to remove the excess salts by precipitation, the mixture was desalinized with the above aqueous solution of Demol-N and aqueous solution of magnesium sulfate, and then stirred and re-dispersed in an aqueous solution containing 92.2 g of ossein gelatin. Emulsion D, comprising tabular silver iodobromide grains having an average grain size of 1.22 µm, an average thickness of 0.29 µm and an aspect ratio of 4.2, was thus obtained. Emulsions E through G, having aspect ratios of 2.5, 7.2 and 12 and average grain sizes of 0.75, 2.2 and 3.6 µm, respectively, were obtained in the same manner as above, except that grain growing pAg and pH were changed as appropriate. To each of the obtained emulsions A through G, the above-mentioned spectral sensitizing dyes A and B, at 300 mg and 15 mg per mol of silver halide, respectively, were added at 55°C. Ten minutes later, appropriate amounts of chloroauric acid, sodium thiosulfate and ammonium thiocyanate were added for chemical sensitization. Fifteen minutes before completion of ripening, silver iodide grains having average grain size of 0.05 µm and containing 0.8 mmol of potassium iodide per mol of silver halide was added. Subsequently, 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene was added at 3 x 10 -2 mol per mol of silver halide, and this mixture was dispersed in an aqueous solution of 70 g of gelatin. After completion of the chemical ripening, emulsions A, B and C were mixed in a 1:6:3 ratio to yield emulsion H, and emulsions A, D and C were mixed in a 1:6:3 ratio to yield emulsion I. To each emulsion, the following additives were added to yield an emulsion layer coating solution. At the same time the following protective layer coating solution was prepared. These emulsions were simultaneously coated on both faces of the support using two slide hopper type coaters at a speed of 80 m per minute so that the amount of silver coated would be 1.9 g/m 2 per face, the amount of gelatin coated would be 2.0 g/m 2 for the emulsion layers, and the amount of gelatin coated would be 1.1 g/m 2 for the protective layer, followed by drying for 2 minutes 20 seconds, to yield a sample. The sample was adjusted to 190% swelling rate (determined by the measuring method described in Japanese Patent O.P.I. Publication No. 206750/1988) by controlling the amount of hardener. In the above-mentioned manner, samples 1 - 14 were prepared in which emulsions and support were changed as given in the later-given table. As the support, the foregoing polyethylene-2, 6-naphthalate (PEN) film of the invention, and a polyethyleneterephthalate film of 100 µm thick for comparison were used. The additives used in the emulsions are as follows: The amounts of addition are shown per mol of silver halide. Protective layer coating solution A protective layer coating solution was prepared as follows: Figures for the amount of addition are shown per liter of coating solution. Preparation of processing solutions Developer Part A Potassium hydroxide 1140 g Potassium sulfite 2451 g Sodium hydrogen carbonate 380 g Boric acid 38 g Diethylene glycol 418 g Pentasodium ethylenetriaminepentaacetate 61 g 5-methylbenzotriazole 1.9 g Hydroquinone 1064 g Water was added to make a total quantity of 9.3 l. Part B (for 38 l finish) Glacial acetic acid 562 g Triethylene glycol 418 g 1-phenyl-3-pyrazolidone 100 g 5-nitroindazole 9.5 g Part mixing While stirring 20 1 of water at 25°C in a 50 liter tank, the above parts A and B were added in this order, and finally water was added to make a total quantity of 38 l. This solution was kept standing at 25°C for 24 hours, after which it was adjusted to pH 10.53 at 25°C by addition of potassium hydroxide or acetic acid. Starter Glacial acetic acid 230 g Potassium bromide 200 g Water was added to make a total quantity of 1.5 l. The above developers were used as replenishers as such. The developing tank solution was used after the above starter was added at 20 ml per l of each developer. The developer replenishing rate was 250 ml per m 2 of the sample according to the present invention. Fixer composition Part A (for 38 l finish) Ammonium thiosulfate 6080 g Disodium ethylenediaminetetraacetate dihydrate 0.76 g Sodium sulfite 456 g Boric acid 266 g Sodium hydroxide 190 g Glacial acetic acid 380 g Water was added to make a total quantity of 9.5 l. Part B (for 38 l finish) Aluminum sulfate (as anhydrous salt) 380 g Sulfuric acid (50% by weight) 228 g Water was added to make a total quantity of 1.9 l. Part mixing While stirring 20 1 of water at 20°C in a 50 liter tank, the above parts A and B were added in this order, and finally water and acetic acid was added to make a total quantity of 38 1 and obtain a pH of 4.30 at 25°C (the Al 3+ content per liter of the fixer was 58.5 mmol). The fixer replenishing rate was 250 ml per m 2 of the sample according to the present invention. Processing Each sample was processed with the above-described developers and fixer, using an automatic processing machine (SRX-502) in the 45-second processing mode, the developing temperature and fixing temperature being 35°C and 33°C, respectively. The sample thus obtained was evaluated as to scratching flaw resistance, roller marks and transportability as follows: Scratching flaw resistance After moisture conditioning at 23°C temperature and 48% RH for 4 hours, the sample was scratched with a nylon brush bearing a 200 g weight on 12 x 14 cm area at a speed of 10 cm/sec, after which it was processed and macroscopically examined for the degree of flaws. Evaluation criteria A: No scratching flaws. B: Almost no light blackened portions. C: Light blackened portions seen, but not problematic for practical use. D: Blackened portions clearly seen, problematic for practical use. E: Numerous blackened lines seen, practical use impossible. Roller marks The unexposed sample film was processed as described above and then macroscopically evaluated as follows: Evaluation criteria A: No pressure spots. B: Light spots seen in film margins, but not problematic for practical use. C: Light spots seen in film center, but not problematic for practical use. D: Dense spots seen in film margins, problematic for practical use. E: Dense spots seen in film center and margins, practical use impossible. Transportability Using the automatic processing machine SRX-502 in the standard 45-second processing mode, 100 consecutive frames of the sample were transported, and the passage time was measured, to obtain the standard deviation. The value for σ, an index of transportability, increases as the dispersion of transport time widens. The results are given in Table 1 below. From Table 1, it is seen that the scratches and roller marks formed in the samples using emulsions D to G and I each comprising silver halide grains with a high aspect ratio are considerably inhibited by the use of the support used in the invention. When emulsion H comprising silver halide grains having an aspect ratio of 1 was used, the scratches and roller marks are not formed, but in this case the benefit of the using of tabular grains such as high sensitivity and high sharpnes of image is not obtained.

Claims: A black and white silver halide photographic light-sensitive material comprising a support and a first silver halide emulsion layer provided on the support, wherein at least 30 % of the total projection area of the silver halide grains contained in said silver halide emulsion layer is occupied by the projection area of tabular silver halide grains having an aspect ratio of not less than 2; and said support comprises polyethylene-(2,6-naphthalate and has a thickness of from 70 µm to 120 µm. The material of claim 1, wherein said tabular silver halide grains have an average grain size of from 0.3 µm to 3.0 µm. The material of claim 1 or 2, wherein said tabular grains have an average aspect ratio of from 2.5 to 20.0. The material of claim 3, wherein said tabular grains have an average aspect ratio of from 3.0 to 10.0. The material of any one of the preceding claims, wherein said tabular grains have an average thickness of from 0.01 µm to 0.5 µm. The material of any one of the preceding claims, wherein at least 50 % of the total projection area of the silver halide grains contained in said silver halide emulsion layer is occupied by said tabular grains. The material of any one of the preceding claims, wherein said polyethylene-2,6-naphthalate has a limiting viscosity number of not lower than 0.4. The material of claim 7, wherein said polyethylene-2,6-naphthalate has a limiting viscosity number of from 0.40 to 0.65. The material of any one of the preceding claims, wherein said polyethylene-2,6-naphthalate has a crystallinity degree of from 35% to 60%. The material of any one of the preceding claims, wherein the variation coefficient of the grain size distribution σ/ r of the silver halide grains contained in the first silver halide emulsion layer is 0.2 or less, wherein a is the standard deviation of grain size distribution and r is the average grain size. The material of any one of the preceding claims, wherein the material comprises a second silver halide emulsion layer on the opposite side of the support to the first silver halide emulsion layer, the first and second silver halide emulsion layers being identical.

Inventors: WADA YASUNORI, WADA, YASUNORI, WADA, YASUNORI, C/O KONICA CORPORATION
Applicants: KONISHIROKU PHOTO IND, KONICA CORPORATION
Application year: 1994
Main classification: G03C1
IPC codes: G03C1, G03C5